Table of Contents

SLIP Connections
PPP Connections
XRemote Connections

Automatic Session Startup—XDMCP Server
Automatic Session Startup—DECwindows Login via LAT
Manual XRemote Session Startup

Enable XRemote Manually
Connect to the Host Computer
Set the Location of the X Display
Start Up Client Applications
Return to the EXEC Prompt
Reenable XRemote Manually

What to Do if a Session Terminates
Establish XRemote Sessions between Servers
Exit XRemote Sessions
XRemote Examples

Connecting an X Display Terminal
Making XRemote Connections between Servers

Telecommuting Service Connections

This chapter describes how to connect devices across telephone lines using SLIP, PPP, or XRemote (the NCD X Windows terminal protocol). Specifically, this chapter contains the following sections:

• SLIP Connections
  
  
• PPP Connections
  
  
• XRemote Connections
  
  

SLIP Connections

You can make a serial connection to a remote host using the Serial Line Internet Protocol (SLIP). Your system administrator can configure SLIP to expect a specific address or to provide one for you. It is also possible to set up SLIP in a mode that compresses packets for more efficient use of the line.

You can issue any of the following commands to terminate an active SLIP session:

PPP Connections

You can make asynchronous connections using the Point-to-Point Protocol (PPP). To start a PPP connection, enter the following command at the EXEC prompt:

Syntax Description

If you specify an address for the TACACS server product, either default or tacacs-server, the address must be the first parameter in the command after you type ppp. If you do not specify an address or enter default, you will be prompted for an IP address or host name. You can enter default at this point.

Any of the following commands will terminate a PPP session:

The following example shows a line that is in asynchronous mode using PPP encapsulation (see Figure 4-1). The PC's name is "ntpc" (assuming that the name "ntpc" is in the domain name system [DNS] so that it can be resolved to a real IP address). The PC must be running a terminal emulator program.

XRemote Connections

You use the XRemote protocol with an X display station and a modem to connect to remote hosts via TCP/IP and LAT. You make connections in one of the following ways:

• Automatically, using the X Display Manager Control Protocol (XDMCP) for TCP/IP networks
  
  
• Automatically, using DECwindows login for LAT networks
  
  
• Manually, using a step-by-step access process
  
  

The following sections outline the steps for starting up XRemote in several typical environments. When possible, use the automated processes. Make sure your system administrator has already configured a path for loading fonts.

Automatic Session Startup—XDMCP Server

If your host computer supports a server product for XDMCP (such as the xdm program included in X11R4 or later), you can use automatic session startup to make an XRemote session connection. To do so, enter the following command:

Automatic Session Startup—DECwindows Login via LAT

If your host computer supports DECwindows login sessions, you can use automatic session startup to make an XRemote session connection. Once the system administrator at the remote host configures support for DECwindows over LAT, you can use the EXEC command xremote lat to initiate the connection. The command has the following syntax:

Manual XRemote Session Startup

If you do not use a host computer that supports XDMCP or LAT, you must use manual session startup. Manual session startup involves several steps:

1. Enable XRemote manually on the server product port.

2. Connect to the host computer.

3. Set the location of the X display.

4. Start up client applications.

5. Return to the EXEC prompt.

6. Enable XRemote manually again on the server product port.

The following sections describe these tasks.

Enable XRemote Manually

To prepare the server product for manual startup, enter the xremote EXEC command at the system prompt.

This command begins the instructions that prompt you through the connection.

Example

The following example illustrates how a successful manual XRemote session begins:

The system replies with a message informing you of your X display location. You will use this information to tell the host the location of your X display server product.

If no clients are found, you see the following message:

Check your hosts to determine whether an error has occurred when the session started. The most likely cause is that there is an improperly specified display location or the host computer did not recognize the name of your server product.

Connect to the Host Computer

You can connect to a host using one of the following connection commands, and log on as usual:

Set the Location of the X Display

At this point, you are logged in to the remote host.

Inform the host computer of your X display location, which the server product provided when you enabled XRemote manually.

For most versions of the UNIX operating system, the X display location is set by using the setenv command to set the DISPLAY environment variable . Refer to your UNIX system's online X(1) manual page for more information.

Start Up Client Applications

Now you start your client applications for your host operating system.

The server product accepts the X connection attempt from the client application and places the client in a dormant state.

Return to the EXEC Prompt

If it is possible to log off the host computer and keep your X clients running in the background, you can do so now. This conserves resources on both the host and the server product that would otherwise be inaccessible until you exited from XRemote state.

If you cannot log off the host computer and keep your clients running, escape back to the server product prompt using the escape sequence (Ctrl-^ X by default).

Reenable XRemote Manually

Begin a manual remote session again (refer to the "Enable XRemote Manually" section earlier in this chapter). If the X clients connected successfully, the session is put into XRemote mode, and the clients complete their startup.

If no clients are found, you see the following message:

Check your hosts to determine whether an error has occurred when the session started. The most likely cause is an improperly specified display location. Or the host computer did not recognize the name of your server product.

What to Do if a Session Terminates

In manual operation, the server product and X terminal remain in XRemote mode until all clients disconnect or a reset request is received from the X terminal.

A session might terminate during startup because you invoked transient X clients that set some parameters and then disconnected (such as xset or xmodmap). There must always be one session open or the connection will be reset.

Establish XRemote Sessions between Servers

A user on an X display server product that does not support XRemote can run the XRemote protocols. An X display server product (such as a PCX, MacX or UNIX workstation) connected to an Ethernet network can dial out through a server product on a conventional modem to access an X client program on a host residing on another network. The server product provides the server-side helper process.

To run XRemote, connect to one of the XRemote ports.

Find out from your administrator whether the connection from your X display terminal is configured as an individual line or a rotary connection.

• To connect to an individual line, use Telnet to connect from the X display terminal to port 9000 plus the decimal value of the line number.
  
  
• To make a rotary connection, use Telnet to connect from the X display server product to port 10000 plus the decimal value of the line number.
  
  

For information about how to configure individual lines and rotary connections, refer to the publications Access and Communication Servers Configuration Guide and the Access and Communication Servers Command Reference.

Figure 4-2 illustrates a configuration in which a display server product is not running XRemote. In this configuration, the server-side XRemote helper is running on Communication Server 1, and the client-side XRemote helper is running on Communication Server 2.

Figure 4-2:
XRemote Session between Communication Servers

Exit XRemote Sessions

You can issue any of the following commands to terminate a terminal session:

XRemote Examples

Use the examples in this section to understand how to make XRemote connections.

Connecting an X Display Terminal

The following example shows a connection from an X display terminal through a server product to a host running client programs.

1. Enter the xremote command at the EXEC prompt:

  dialup> xremote

2. Read and follow the instruction from the host:

3. Connect to the client:

4. Log on at the prompt:

5. At the client prompt, enter the display name from step 2 and the xterm command:

6. Disconnect from the client:

7. Begin the XRemote session:

The server product and X terminal stay in XRemote mode until either the display manager terminates the session or a reset request is received from the X terminal:

Making XRemote Connections between Servers

This section provides two examples of XRemote connections between server products.

The following steps show how an XRemote connection is established for a configuration like the one shown in Figure 4-2. These steps assume that the administrator has set the user's display environment variable to identify the user's X display terminal.

1. From the PCX, MacX, or UNIX machine in Figure 4-2, the user connects to port 9003 on communication server 1. If your administrator has configured a rotary number 7, the user connects to port 10007. For more information about rotary groups, refer to the Access and Communication Servers Configuration Guide and the Access and Communication Servers Command Reference publication.

2. Communication server 1 connects the user to a modem.

3. The modem calls communication server 2.

4. The user enters xremote at the communication server 2 prompt.

5. The user connects to the remote host from communication server 2 using the telnet command.

6. The user starts the X client program that will run on the remote host and display on the X display server product (PCX, MacX, or UNIX host).

7. The user escapes from the remote host back to the communication server 2, or logs out if clients were run in the background, and enters xremote again at the communication server 2 prompt.

The following example shows the steps to make an XRemote connection between server products. The number 9016 in the first line of the display indicates a connection to individual line 16. If the administrator had configured a rotary connection, the user would enter 10000 plus the number of the rotary instead of 9016.

1. Enter the telnet command to make the connection:

2. Supply the password for TACACS verification:

3. Dial in to the remote system using the modem, and then log on:

4. Enter the xremote command at the EXEC prompt, then follow the instructions from the host:

5. Connect to the client:

6. At the client prompt, enter the display name from step 4 and the xterm command:

7. Disconnect from the client:

8. Begin the XRemote session:

Once the connection is closed by the foreign host, the Xterm window appears on the local workstation screen:

Posted: Mon Oct 21 12:33:21 PDT 2002
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